1. Field of the Invention
The invention lies in the field of medical diagnostic procedures and devices.
2. Background of the Prior Art
There is a need for obtaining small samples of human interstitial fluid from the skin for the purpose of analyzing this fluid for biologically relevant molecules and electrolytes that may be found therein. More particularly, there is a need for carrying out the process of releasing and collecting the interstitial fluid for glucose measurements which is useful for diabetics. The most common current techniques for obtaining body fluid for glucose measurements is done by pricking the skin with a sharp object to create a small drop of blood. This sample can then be collected and analyzed in a test kit to determine the glucose contents. The process of pricking the skin to produce fluid samples is obviously undesirable because of the pain it creates. It would be desirable to have a more painless method of collecting and releasing interstitial fluid for this and other purposes.
This application discloses a new method for releasing interstitial fluid from skin for collection or measurement, such as for glucose determinations. The method avoids the psychological and physical pain of pricking the finger with a sharp instrument.
A carrier film having at least one opening and preferably a series of spaced openings is provided for use with a laser which produces a laser beam. The openings in the carrier film contain a meltable absorber substance selected to absorb energy from the laser beam and may include an aperture in the carrier film adjacent the opening or more than one aperture adjacent a plurality of openings. The carrier film has a base layer having the openings for the meltable absorber substance and a cover layer which covers one open side of the openings to form a well filled with absorber substance, having one open side. The carrier film is placed over the skin with the open side of the opening containing the meltable absorber substance positioned facing the skin. The laser is positioned over the carrier film with the beam it produces directed upon the absorber substance and passing through the cover film of the carrier.
Upon energizing the laser to produce the laser beam, the meltable absorber substance is melted and substantially instantaneously ejected from the opening in the carrier film and then transferred with velocity to the surface of the skin where it becomes a spot capable of absorbing laser energy. The carrier film can be moved away or indexed to the aperture whereby the laser can be employed (or a different laser) to project a laser beam onto the spot of absorber substance on the skin thereby raising a tiny blister containing interstitial fluid on the skin in the area where the spot was formed. The interstitial fluid is then available by various conventional means for collection by breaking the blister and taking the interstitial fluid for testing or analysis.
A method of making the carrier film is disclosed. A carrier film base member with spaced openings is supported on a flat support and loaded with meltable absorber substance from a digitally operated heated printhead of the type used for xe2x80x9cjettingxe2x80x9d materials, similar to an ink jet for a computer printer. Indexing of the carrier film strip or the printhead sequentially fills the openings with the absorber substance. A cover is preferably adhesively laminated over the openings containing the meltable absorber substance creating a well-like opening that has an open side from which the material will be ejected when activated by a suitable laser beam. Both the cover strip and adhesive are selected to allow the laser beam to be focused on the meltable absorber substance inside the openings. A cover strip may be made in a batch process or, for example, in a reel-to-reel continuous process using flexible film technology. The carrier material is preferably a laminated carrier film although it is conceivable that a blind opening could be produced in a film having the requisite clarity to passage of laser energy in the nature of a blind opening.
The well-like openings from which the meltable absorber material will be ejected may include a nozzle which is smaller than the opening itself and a gas bubble created in the back of the opening by the manner in which the opening is filled with the absorber substance. Upon melting of the absorber substance in response to impingement by a laser beam, the nozzle and gas bubble enhance the ability of the carrier strip to eject a melted droplet of the absorber substance with a certain amount of velocity onto the skin where it flattens to form a spot for subsequent steps.
It is easy to visualize a relatively small machine containing a carrier film with spaced openings and apertures which can be placed over a patient""s arm for analysis. First the laser is triggered to deposit a spot of the absorber substance on the skin, then the carrier film is indexed to an opening whereby the same laser could impact the spot on the skin to form the blister which raises interstitial fluid from the skin. Collection of the interstitial fluid could be mechanized or simply taken from the tiny blister by conventional means.